Field of the Invention and Related Art Statement
The present invention relates to a process for preparing hyaluronic acid with a microbe capable of producing hyaluronic acid (hereinafter referred to as a "hyaluronic acid-producing microbe"). More specifically, this invention relates to a process for preparing hyaluronic acid comprising incubating a hyaluronic acid-producing microbe in a culture medium containing blood serum, a bacteriolytic enzyme, a surface active agent, or a bacteriolytic enzyme plus a surface active agent to yield and accumulate hyaluronic acid in the culture medium, and isolating the same.
Hyaluronic acid exists in connective tissues such as joints, vitreous bodies, umbilical cords, cartilages, skins, and combs of fowls as a constituent thereof, and fulfils important functions such as flexibility and structure maintainence of tissues, and metabolic regulation of cells. Hyaluronic acid is a very large high molecular weight polymer, and a solution thereof has a high viscoelasticity and a water-holding function. Therefore, it has a wide variety of uses in cosmetics, medicines for wounds, eye waters, medicines for arthritis.
Hyaluronic acid has heretofore been commercially obtained by a method of extraction thereof from combs of fowls, vitreous bodies of bovine eyes, umbilical cords, cetacean cartilages, or the like. However, hyaluronic acid obtained from living bodies by the extraction method is in the form of a complex formed with a protein or a mucopolysaccharide such as chondroitin, and hence, needs complicated steps for separation and purification. Furthermore, since it is present in most cases in the form of a mixture with hyaluronidase, there has been drawbacks in that such a hyaluronic acid may be decomposed in the course of extraction and purification steps to reduce its molecular weight, and as consequent effects thereof its viscosity and water-holding property are lowered. In view of the above, an attempt to prepare hyaluronic acid by the cultivation method has been disclosed in Japanese Patent Laid-Open Specification No. 56692/1983. However, it is a difficult point of this method that the productivity of hyaluronic acid is poor.
The inventors of the present invention have made intensive investigations in order to solve the above-mentioned problem involved in the preparation of hyaluronic acid. As a result, it has been found that use of a culture medium containing blood serum added thereto or a culture medium containing a bacteriolytic enzyme and/or a surface active agent added thereto in incubation of a hyaluronic acid-producing microbe largely increases the productivity of hyaluronic acid. The present invention has been completed based on this finding.